With the development of mobile communications technologies, a user has increasingly high demands for a network bandwidth. To enhance efficiency of transmitting network data, a low power node (LPN, Low Power Node) may be introduced in a macro cell (macro cell) to form a low power cell, for example, a micro cell (micro cell), a pico cell (pico cell), or a femto cell (femto cell), to enable these low power cells to cover service hotspot areas or areas out of cell coverage. In this way, when a user equipment (User Equipment, UE) moves to these areas, a service of the UE may be handed over to these low power cells, so as to implement service offloading or coverage compensation.
A specific process that UE is handed over to and enters a new cell is generally as follows: The UE receives measurement configuration information of a communications node (that is, a source communications node) of a source cell in which the UE is located, where the measurement configuration information includes measured frequency information. According to the received frequency information, the UE detects a reference signal of a target cell corresponding to the frequency information, and measures the target cell whose reference signal is detected. The UE reports a measurement result to the source communications node, and after determining, according to the measurement result, to perform cell handover, the source communications node initiates a handover request to a communications node (that is, a target communications node) of the detected target cell. The target communications node decides, according to a network condition such as load, interference, and a transmission network bandwidth of the target cell, whether to accept a service of the UE. If the service cannot be accepted, the target communications node sends information about a handover rejection or a handover failure to the source communications node, or if the service can be accepted, the target communications node sends infatuation about a handover agreement or a handover acknowledgment to the source communications node. FIG. 1 is a schematic diagram of UE being handed over between different cells in a heterogeneous network.
In the prior art, when a target cell provides a service, a target communications node of the target cell continuously sends a reference signal. When the target cell turns off the service, a transmitter of the target cell is closed, and the target communications node also no longer sends the reference signal. Because when the target cell provides the service, the reference signal of the target cell is sent continuously, even if load of the target cell is very heavy, UE within a coverage area of the reference signal can also detect the target cell. After completing measurement of the target cell, the UE reports a measurement result to a source communications node. After analyzing the measurement result of the UE and determining to perform cell handover, the source communications node sends a handover request to the target communications node. However, when receiving the handover request, the target communications node may reject the handover request because the load of the target cell is excessively heavy. In this way, a previous process that the UE performs measurement and reporting, a process that the source communications node receives and analyzes the measurement result, and a process of interactions between the source communications node and the target communications node become invalid work. Especially, when the target cell is deployed in a hotspot area, because of a relatively large quantity of UEs, a very large amount of invalid work is caused. FIG. 2 is a schematic diagram of a target cell rejecting access by UE because load of the target cell is excessively heavy.
The foregoing invalid work increases unnecessary signaling overhead between the UE and the source communications node and between the source communications node and the target communications node, and increases a running burden of analyzing the measurement result by the source communications node; moreover, because the source cell cannot perform scheduling for the UE in a measurement process, normal information transmission cannot be performed. The foregoing invalid measurement process severely affects a throughput of the UE.
In addition, in the prior art, once a reference signal starts being sent, a sending state of the reference signal no longer changes.